Optical device, such as optical scanner, employs an optical path folding device to reflect an incident light to a lens for forming a light image signal, and uses a charge coupled device (CCD) to covert the light image signal to electronic signals for being stored and processed in electric devices. Optically, it needs a certain length of optical path to form a clear light image. In order to reduce the size of an optical device, the conventional optical path device usually has several reflection mirrors to fold optical paths. Hence, the number, size, and relative positions of the reflection mirrors of the optical path device directly affect the size and weight of the optical path device, and indirectly affect the size and weight of an optical device.
A conventional optical scanner usually has four pieces of reflection mirrors, and each reflection mirrors reflects an incident light projected by a light source before the light is focused and reaches a charge coupled device. However, under the influence resulted from the tendency of compact and light-weighted electronic products, the requirements of volume and weight for the electronic products are raised increasingly. Therefore, how to effectively reduce the size and weight of an optical path device, and increase the flexibility for fitting various lenses to make optical devices gain great volume efficiency, has become a very important subject in the current optical device industry.